What types of events lead to storm surge and inundation?

Storm surge and inundation can occur as a result of tropical cyclones or extra-tropical storms. Tropical cyclones are storms that originate in the tropics, and are categorized by the rotational winds produced and in relation to the damage they typically cause, according to the Saffir-Simpson Scale.

A tropical cyclone can progress through some or all of the above stages during its lifecycle<97>beginning after it first forms as a tropical depression, or after it reaches its maximum intensity and begins to dissipate.&nbsp; Many of the most destructive storms to reach the CB or its watershed during the recent past (approximately last 100 years), however, appear to have either been in the process of degrading, or quickly degraded once they made landfall. Thus, the CB has never experienced a tropical cyclone making landfall that was greater in strength than a Category 1 or weak Category two Hurricane. Never-the-less there are clear historical indications that tropical depressions, storms, and low category hurricanes have caused significant damage and loss of life in the CB region.

The following is a brief history of tropical cyclones that have affected the Virginia portions of the CB. Many of these same storms had similar impacts on Maryland portions of the CB or its watershed (Source - National Weather Service, Wakefield Office http://weather.gov/akq).

Since 1871, 123 hurricanes and tropical storms have affected Virginia taking 228 lives and costing the commonwealth over a billion dollars in damages. The eye or center of 69 tropical cyclones has tracked directly across Virginia. Eleven have made landfall on or close (within 60 miles) to the Virginia Coast. Virginia averages one storm a year. Overall, Hurricanes come close enough to produce hurricane force winds approximately three times every 20 years. Two or three times a century winds and tides produce considerable damage and significantly threaten life. Three known storms have been powerful enough to alter coastal features. Also this recent history indicates up to no more than four years have gone by with no storms (for example, 1919 through 1922), while in other individual years up to seven storms have occurred, with storms coming just days or weeks apart (for example, in 1933). As the following detailed chronology of just the known 20th and 21st century storms that have hit Virginia indicates, the destruction of these storms comes in varied forms, including storm surge, river flooding, and high winds, including tornadoes (MLLW refers to Mean Lower Low water which is the mean of the lowest of the low tide values).